Dispersion ebullator



April 1, 1969 A. w. LINKE ET AL msrs'asiou EBULLATOR Filed April 26.1966 INVENTORS ALVIN W. LIN KE JOHN H. CANTLI United States PatentOfiice 3,435,682 Patented Apr. 1, 1969 Filed Apr. 26, 1966, Ser. No.545,469 Int. Cl. G01k 5/28 US. Cl. 73368.2 20 Claims ABSTRACT OF THEDISCLOSURE A thermally responsive power element comprises an expansiblemember having a tube connected at one end thereto and in communicationwith the interior thereof. The tube is otherwise closed and contains avolatile liquid which is adapted to boil and expand the expansiblemember when any portion of the tube is subjected to a given temperature.The liquid contains particles of non-Wettable material, such aspolytetrafluoroethylene. The particles are of such a size that they areheld in suspension and dispersed throughout the liquid and are effectivein promoting ebullation of the liquid at a given temperature.

This invention relates to improvements in thermally responsive powermeans of the type comprising a liquidcontaining expansible chamberhaving a movable wall which is distended when any of the liquid isvaporized by an increase in temperature thereof. The movable wall may beutilized to actuate a control device such as an electric switch orvalve. More specifically the present invention is directed to theaforesaid thermally responsive power means which comprises anon-wettable material of small particle size dispersed in the liquidcontained in said expansible chamber, which combination effectsthermally, reliable, efiicient, and economical means for actuating thecontrol device such as an electric switch or valve.

Thermally responsive power means of the general type described areknown, but prior to our invention the liquid therein would not vaporizeconsistently at predetermined temperatures throughout a considerablepassage of time. Experience has shown that minute quantities of gas inthe liquid will cause the liquid to vaporize at predeterminedtemperatures; however, this gas eventually separates from the liquid andthe remaining pure liquid will not vaporize unless it is heated to anunpredictable temperature ap preciably above that at which the impureliquid vaporizes.

The present invention is an improvement over the device disclosed in US.Patent No. 3,163,045, issued on Dec. 29, 1964, an important feature ofsaid patent being directed to an abraided Teflon(polytetrafiuoroethylene) coated wire extending through a capillary tubecomprising an elongated temperature sensing member and containing; avolatile liquid for operating a control device, for example, theabraided coating assuring boiling of the liquid at a predeterminedtemperature. The present invention provides more economical, simple,efficient and reliable means for assuring boiling of the liquid at anypoin throughout the entire length of the capillary tube than thatdisclosed in the aforementioned patent.

An object of the present invention is the provision of a thermallyresponsive power means of the type described in which fine particles ofa non-wettable material, such as polytetrafluoroethylene, is dispersedthroughout the body of the volatile liquid so that the liquid or anyportion thereof subjected to its volatilizing temperature vaporizesconsistently at a definite temperature. In a preferred form of theinvention, the liquid includes water, and the non-Web table material ispolytetrafiuoroethylene, known commercially as Teflon, a long-chainsynthetic polymer. Other non-wettable materials may be long-chainsynthetic polymeric amids, some members of which are known commerciallyunder such trade names as nylon, Dyncl, Orion, etc., manufactured by theDu Pont Company of Wilmington, Del.

Another object of this invention is the provision of an improved powermeans of the foregoing character wherein the expansible chamber includesa substantial length of a relatively small diameter tubular sensingmember containing at least a portion of the liquid fill and having thenon-wettable material in the interior thereof and distributed throughoutthe length of the tubular member in the form of a dispersion of minuteparticles thereof. For eX- ample, the liquid may include water, glycols,alcohols, etc., or mixtures of the same. The non-wettable material maybe of the character set forth above such as a dispersion ofpolytetrafluoroethylene plastic (Teflon) having an average particlediameter size in the range of about .05 micron and 0.5 micron in thetube and extending throughout its length, whereby the liquid in allsections of the tube is in contact with the non-wettable material sothat when any relatively short zone or segment of the tubular member isheated to raise the temperature of the liquid in the segment apredetermined degree, the portion of the liquid in this segment willvaporize and cause a substantial increase in pressure and distend themovable wall of the chamber even when the major portion of the liquidremains unvaporized.

Yet another object of this invention is the provision of an improvedcontrol device comprising a switch, valve, or the like, operable by themovable wall of an expansible chamber connected to a tubular temperaturesensing member containing a liquid comprising water, organic liquids,such as ethylene glycol, methyl alcohol, etc., or a mixture of water andanother volatile liquid and having a dispersion material of relativelyfine average particle diameter size of a non-wettable material disposedin the tubular member and extending substantially throughout the lengththereof.

Another object of this invention is the provision of a dispersedactivating non-wettable material dispersed in said liquid for improvedcontact of said liquid with said non-wettable material for enhancedcontrol of the power sensing device.

Another object of the present invention is directed to the product of aresin dispersed in a liquid fill which functions for the purposedisclosed herein.

Other objects and advantages of this invention will become apparent fromthe following detailed description of a presently preferred embodimentthereof, taken in conjunction with the accompanying sheet of drawingforming a part of this specification and in which:

FIG. 1 is a longitudinal sectional view of a control device, embodyingthe present invention, with a portion of the tubular member thereofshown in a magnified scale;

FIG. 2 is an end view of the device of FIG. 1 taken along line 22 on aslightly reduced scale;

FIG. 3 is a sectional view taken along line 3 3 of FIG. 1; and

FIG. 4 is a sectional view of an enlarged scale taken along line 44 ofFIG. 1.

In the form of the invention shown in the drawings and describedhereinafter, the invention is embodied in a thermally responsive controlswitch device 10, although it will be understood that the invention maybe embodied in devices having other control functions such as athermally responsive control valve, or the like.

Referring to FIGS. 1, 2 and 3, control device 10 is seen to comprise acylindrical or cup-shaped housing 12 formed of a suitable insulatingmaterial such as Bakelite. A pair of stationary contact members 13 and14 extend through the side wall 12a of housing 12 and having their innerends riveted to bosses 12b and as by rivets 16. The outer ends ofcontact member 13 and 14 serve as switch terminals for the connection ofwires such as 18 and .19 secured thereto by binding screws 20 and 21. Amovable bridging contact 24 is mounted for movement with an axiallymovable operating rod 25 which is slidably received in a guide bore 26formed in housing 12. Bridging contact 24 is normally biased in bridgingengagement with contacts 13a and 14a, on contact members 13 and 14respectively, by a bowed leaf spring 28. Operating rod 25 extendsthrough an opening in a guide disc 30 and is adapted to be moved by theaction of a flexible diaphragm 31 forming part of a thermally responsivepower means generally indicated at 32.

Power means 32 comprises a cup-shaped member 33 having mounting ears33a, and in which the open end of housing 12 is received and retained byan inwardly directed tab 33b and a spring clip 330 which projectsthrough one wall of cup 33. Diaphragm 31 is welded about its peripheraledge to the bottom of cup-shaped member 33 adjacent wall 33d thereof,thereby forming a narrow chamber 34. A nipple 35 is spot welded orbrazed in a central opening of member 33 and receives one end of acapillary tube 36. The opposite end 36a of the tube is sealed and thetube and chamber 34 contain a liquid fill 37 comprising a mixture ofwater and volatile liquid such as methyl alcohol, which liquid fill willbe discussed more fully hereinafter.

Diaphragm 31 is formed with convolutions 31a em bossed therein whichcause it to have an over-center snap action when flexed, and ifunrestrained would tend to remain in the position of FIG. 1 in which rod25 is moved to the right and the switch contacts are separated. Chamber34 and tube 36 are, however, charged with liquid fill 37 at a pressuresubstantially less than the ambient atmospheric pressure acting ondiaphragm 31, so that at temperatures less than the boiling point of theliquid the diaphragm is held in the dotted line position of FIG. 1, withthe switch contacts closed. It will be recognized that either uponboiling of the liquid fill 37 or upon a leak developing in the system,the pressure in chamber 34 will increase and permit diaphragm 31 to snapto its full line position and open the contacts so as to deenergize acircuit connected thereto. Thus, the control device is not only adaptedto actuate the switch contact upon predetermined increases intemperature along the tubular member 36, but also incorporates afail-safe feature effecting opening of the contacts in the event of lossof fluid-tight integrity in the thermally responsive power means 32. Inthe present example, the diaphragm 31 snaps out upon a decrease ofvacuum in the chamber 34 to Within a range of about 3 to 8 inches ofmercury, and will snap in or reset when the vacuum is increased to about13 to 18 inches of mercury. It will be noted that rod 25 extends beyondthe wall of housing 12 as shown at 25a and slideable therein so that therod 25 can be operated manually when desired or found necessary forresetting the flexible diaphragm 31 to its dotted line position of thedrawing.

Included also in tube 36 is a dispersion of said nonwettable resinmaterial preferably, but not limited thereto, of polytetrafluoroethyleneplastic particles 40 as shown in FIGS. 1 and 4. For convenience, inquantity production of devices embodying the invention, the dispersionmay be introduced into the liquid prior to charging the liquid into thetube, and this is accomplished by preparing a convenient batch volume ofthe particular liquid to be employed and then adding a small quantity ofa dispersion of the particles in tap or distilled water, for example,and the liquid and the dispersion are then thoroughly mixed, as bystirring. The liquid is then introduced into the capillary tubes 36 ofthe individual control devices in the usual manner. The capillary tube36 is then fused as at 36a.

The liquid fill in another example may comprise a mixture of water andmethyl alcohol, with water constituting about 65% of the mixture andmethyl alcohol constituting about 35% of the mixture. This mixture, whenconfined at the previously mentioned pressure in the capillary tube 36with dispersed Teflon as the activating agent, will vaporize or boil atF. thereby flexing diaphragm 31 for operation of the switch device. Itshould be understood that while the non-wettable dispersed materialpreferably comprises Teflon, other materials may be resins that belongto the family of long-chain synthetic polymeric amides such as nylon,Orlon, dynel, etc., other materials which conform to the class ofnon-wettable materials would function for the purpose of the presentinvention.

While resin dispersions in liquid fills may be produced commercially, anexample only of such a dispersion for the present purpose would compriseaqueous dispersed Teflon therein to the extent of about 59% to 61%solids and having about 5.5% to about 6.5% of a non-ionic wetting agentin water. Such a mixture would consist of about 7.5 pounds of powderedTeflon per gallon of Water. It is also to be noted that such dispersionswill settle somewhat on prolonged standing, but can be redispersed bymild agitation. In addition, the dispersion should be protected againstfreezing, which would cause an irreversible coagulation. Anothereffective liquid fill besides water, per se, could be prepared usingdipropylene glycol with or without any additions, and Teflon.

Mixtures of water and other substances such as methyl alcohol, ethyleneglycol, etc., may be used in different proportions to provide actuationat other temperatures. For example, water mixtures containing the listedpercentages of ethylene glycol or methyl alcohol will provide responseat the following temperatures:

F. Methyl alcohol, 6% Ethylene glycol, 51% 210 Ethylene glycol, 82% 240Ethylene glycol, 89% 260 Ethylene glycol, 94% 285 In addition, extensiveexperimentation has shown that certain pure liquids which have beensubject to the problem of unpredictable superheating heretofore may beused as the fill and will provide reproducible results repeatedly whenin the presence of the Teflon, or other non-wettable materials. Forexample, pure distilled water may be used as the fill, and under thementioned pressures will result in an operating temperature of 205 F.,and triethylene glycol will result in an operating temperature of 550 F.However, such liquids with, for example, only the added powdereddispersion therein as noted above, in a concentration of about 0.1% byvolume, will produce far better results, economically, efiiciently, andreliably than the device of the previously referred to patented devicewherein the capillary tube has an inserted steel wire core having anon-wettable ma terial such as Teflon tape wrapped around said wirecore.

While it is not fully understood why the use of the above liquid fillsin the presence of Teflon have been successful in overcomingsuper-heating of the liquid fill, when confined in a capillary tube, forexample, it is believed that the resistance of Teflon to wetting bywater or other vaporizing liquids creates a surface condition betweenthe liquid and the dispersed particles of said Teflon which permitsvapor bubbles {$0 readily form before the boiling point is actually reaed. Thus, when the boiling point is reached, there are in' existencevapor filled interfaces at which the boiling can occur.

From the foregoing detailed description, it will be recognized that thisinvention has provided an improved thermally responsive device Which isactuable by attainment of a predetermined temperature at any givenlength along the temperature sensing capillary tube and which is notsubject to averaging of the temperatures therealong. It will also berecognized that the use of a mixture of water and other volatile liquidin the presence of a dispersion of said non-wettable material, of whichTeflon is most preferable, eliminates any likelihood of super-heatingand failure of the control device to be actuated.

Although the invention has been described in considerable detail withreference to a preferred form of control device embodying the invention,it is understood that the invention is not limited thereto.

Having thus described our invention, we claim:

1. A thermally responsive power means comprising:

an expansible hollow element,

a volatile liquid in said element, and

particles of non-wettable material of a diameter size rendering theparticles capable of suspension in said liquid and dispersedtherethroughout.

2. A thermally responsive power means as defined in claim 1 wherein saiddispersed non-wettable material is a synthetic resin.

3. A thermally responsive power means as defined in claim 1 wherein thenon-wettable material comprises a long-chain synthetic polymeric amide.

4. A thermally responsive power means as defined in claim 1 in whichparticles of said non-wettable material dispersed throughout said liquidhave diameters no greater than about 0.5 micron.

5. A thermally responsive power means as defined in claim 4 wherein saiddispersed non-wettable material is a synthetic resin.

6. A thermally responsive power means as defined in claim 4 wherein thenon-wettable material comprises a long-chain synthetic polymeric amide.

7. A thermally responsive power means as defined in claim 4 wherein saiddispersed material comprises polytetrafluoroethylene.

8. A thermally responsive power means as defined in claim 4 wherein saidliquid comprises a mixture of water and ethylene glycol.

9. A thermally responsive power means as defined in claim 4 wherein saidliquid comprises a mixture of methyl alcohol and water.

10. A thermally responsive power means comprising an expansible hollowelement, a volatile liquid in said element, and particles ofnon-wettable material having an average particle diameter size of fromabout .05 micron to about 0.5 micron.

11. A thermally responsive device as defined in claim 10 and comprisinga tubular sensing element communicating with the interior of said hollowmember and containing said liquid, said material comprising dispersedpolytetrafiuoroethylene.

12. A thermally responsive power means as defined in claim 10 whereinsaid dispersed material comprises polytetrafluoroethylene.

13. A thermally responsive power means as defined in claim 12 andwherein said liquid comprises water.

14. A thermally responsive power means as defined in claim 12 whereinsaid liquid comprises a mixture of water and ethylene glycol.

15. A thermally responsive power means as defined in claim 12 whereinsaid liquid comprises a mixture of methyl alcohol and water.

16. A thermally responsive power means as defined in claim 15 whereinsaid dispersed material comprises a long-chain synthetic polymericamide.

17. A thermally responsive power means as defined in claim 15 whereinsaid volatile liquid comprises a glycol.

18. A thermally responsive power means as defined in claim 15 whereinsaid volatile liquid comprises an alcohol.

19. A thermally responsive power means as defined in claim 15 whereinsaid volatile liquid comprises water.

20. A thermally responsive power means as defined in claim 15 whereinsaid expansible element and said tube being filled with a mixture ofwater and another volatile liquid.

References Cited UNITED STATES PATENTS 3,163,045 12/1964 Kaveckas et al.73-368.2

LOUIS R. PRINCE, Primary Examiner.

WM. HENRY II, Assistant Examiner.

US. Cl. X.R.

